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[CRYPTO] ctr: Add countersize
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This patch adds countersize to CTR mode.
The template is now ctr(algo,noncesize,ivsize,countersize).

For example, ctr(aes,4,8,4) indicates the counterblock
will be composed of a salt/nonce that is 4 bytes, an iv
that is 8 bytes and the counter is 4 bytes.

When noncesize + ivsize < blocksize, CTR initializes the
last block - ivsize - noncesize portion of the block to
zero.  Otherwise the counter block is composed of the IV
(and nonce if necessary).

If noncesize + ivsize == blocksize, then this indicates that
user is passing in entire counterblock. Thus countersize
indicates the amount of bytes in counterblock to use as
the counter for incrementing. CTR will increment counter
portion by 1, and begin encryption with that value.

Note that CTR assumes the counter portion of the block that
will be incremented is stored in big endian.

Signed-off-by: Joy Latten <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>
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@herbertx
Joy Latten authored and herbertx committed Jan 10, 2008
1 parent d3e7480 commit 41fdab3
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Showing 2 changed files with 25 additions and 15 deletions.
32 changes: 21 additions & 11 deletions crypto/ctr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ struct ctr_instance_ctx {
struct crypto_spawn alg;
unsigned int noncesize;
unsigned int ivsize;
unsigned int countersize;
};

struct crypto_ctr_ctx {
Expand Down Expand Up @@ -186,7 +187,6 @@ static int crypto_ctr_crypt(struct blkcipher_desc *desc,
unsigned long alignmask = crypto_cipher_alignmask(child);
u8 cblk[bsize + alignmask];
u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1);
unsigned int countersize;
int err;

blkcipher_walk_init(&walk, dst, src, nbytes);
Expand All @@ -198,18 +198,18 @@ static int crypto_ctr_crypt(struct blkcipher_desc *desc,
memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize);

/* initialize counter portion of counter block */
countersize = bsize - ictx->noncesize - ictx->ivsize;
ctr_inc_quad(counterblk + (bsize - countersize), countersize);
ctr_inc_quad(counterblk + (bsize - ictx->countersize),
ictx->countersize);

while (walk.nbytes) {
if (walk.src.virt.addr == walk.dst.virt.addr)
nbytes = crypto_ctr_crypt_inplace(&walk, child,
counterblk,
countersize);
ictx->countersize);
else
nbytes = crypto_ctr_crypt_segment(&walk, child,
counterblk,
countersize);
ictx->countersize);

err = blkcipher_walk_done(desc, &walk, nbytes);
}
Expand Down Expand Up @@ -251,6 +251,7 @@ static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
struct ctr_instance_ctx *ictx;
unsigned int noncesize;
unsigned int ivsize;
unsigned int countersize;
int err;

err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
Expand All @@ -270,9 +271,17 @@ static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
if (err)
goto out_put_alg;

/* verify size of nonce + iv + counter */
err = crypto_attr_u32(tb[4], &countersize);
if (err)
goto out_put_alg;

/* verify size of nonce + iv + counter
* counter must be >= 4 bytes.
*/
err = -EINVAL;
if ((noncesize + ivsize) >= alg->cra_blocksize)
if (((noncesize + ivsize + countersize) < alg->cra_blocksize) ||
((noncesize + ivsize) > alg->cra_blocksize) ||
(countersize > alg->cra_blocksize) || (countersize < 4))
goto out_put_alg;

inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
Expand All @@ -282,20 +291,21 @@ static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)

err = -ENAMETOOLONG;
if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
"ctr(%s,%u,%u)", alg->cra_name, noncesize,
ivsize) >= CRYPTO_MAX_ALG_NAME) {
"ctr(%s,%u,%u,%u)", alg->cra_name, noncesize,
ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
goto err_free_inst;
}

if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"ctr(%s,%u,%u)", alg->cra_driver_name, noncesize,
ivsize) >= CRYPTO_MAX_ALG_NAME) {
"ctr(%s,%u,%u,%u)", alg->cra_driver_name, noncesize,
ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
goto err_free_inst;
}

ictx = crypto_instance_ctx(inst);
ictx->noncesize = noncesize;
ictx->ivsize = ivsize;
ictx->countersize = countersize;

err = crypto_init_spawn(&ictx->alg, alg, inst,
CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
Expand Down
8 changes: 4 additions & 4 deletions crypto/tcrypt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -969,9 +969,9 @@ static void do_test(void)
AES_XTS_ENC_TEST_VECTORS);
test_cipher("xts(aes)", DECRYPT, aes_xts_dec_tv_template,
AES_XTS_DEC_TEST_VECTORS);
test_cipher("ctr(aes,4,8)", ENCRYPT, aes_ctr_enc_tv_template,
test_cipher("ctr(aes,4,8,4)", ENCRYPT, aes_ctr_enc_tv_template,
AES_CTR_ENC_TEST_VECTORS);
test_cipher("ctr(aes,4,8)", DECRYPT, aes_ctr_dec_tv_template,
test_cipher("ctr(aes,4,8,4)", DECRYPT, aes_ctr_dec_tv_template,
AES_CTR_DEC_TEST_VECTORS);

//CAST5
Expand Down Expand Up @@ -1160,9 +1160,9 @@ static void do_test(void)
AES_XTS_ENC_TEST_VECTORS);
test_cipher("xts(aes)", DECRYPT, aes_xts_dec_tv_template,
AES_XTS_DEC_TEST_VECTORS);
test_cipher("ctr(aes,4,8)", ENCRYPT, aes_ctr_enc_tv_template,
test_cipher("ctr(aes,4,8,4)", ENCRYPT, aes_ctr_enc_tv_template,
AES_CTR_ENC_TEST_VECTORS);
test_cipher("ctr(aes,4,8)", DECRYPT, aes_ctr_dec_tv_template,
test_cipher("ctr(aes,4,8,4)", DECRYPT, aes_ctr_dec_tv_template,
AES_CTR_DEC_TEST_VECTORS);
break;

Expand Down

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